Construction methods using jet grouting have been used in a variety of applications where structural strengthening or reinforcement of the earth is required. For example, jet grouting has been applied to build structures used for underpinnings, landslide stabilization, earth tie-downs, earth anchors, embankment consolidation and excavation support for tunnels and above ground structures.
Jet grouting generally makes use of high pressures on the order of 6,000-8,000 psi to inject cementitious grout fluids into the soil at high velocities. A typical application involves drilling or otherwise forming a bore and then injecting grout at high pressure into the walls of the bore to cut into and mix with the soil and other native materials around the bore. After the grout has been allowed to harden, a column is formed in the bore and the soil immediately surrounding it. The column can be used as structural support for a building or other structure erected on previously unstable soil. One of the principal advantages of the jet grouting process is that a relatively large diameter column can be formed with only a relatively small diameter bore required. The high injection pressure of the grout carries it well into the soil around the drilled hole. In this manner, the grouting pressure effectively increases the bore size and results in a large and strong column. At the same time, drilling costs are incurred for only a relatively small diameter hole.
Using reinforcing bar and other reinforcement materials in subterranean columns of this type is known to increase the column strength markedly. However, the application of reinforcing materials has been difficult to accomplish from a practical standpoint. Typically, a number of additional steps in the construction process are required, and they can result in significantly increased costs due to delay, labor costs, and the need for additional equipment to install the reinforcing elements. Accurate placement of the reinforcement in the column has also been a problem. If the reinforcement is improperly positioned, the reinforcing effect is reduced accordingly.